Without disclosing North Korea's terms, the IAEA spokeswoman Gill Tudor said it had received the invitation on Friday. That was the same day Pyongyang announced plans to launch a satellite on a rocket, a move that Washington has suggested could jeopardise a nuclear moratorium deal reached with the United States last month.

The IAEA's announcement came hours after Ri Yong-ho, a senior North Korean nuclear negotiator, said Pyongyang was sending invitations to agency inspectors as part of implementing the moratorium agreement.

The US state department spokeswoman Victoria Nuland said Washington had not been told of a formal invitation to the IAEA from North Korea – but said such a move would be positive, while repeating America's reservations about the planned satellite launch.

"Obviously there's benefit for any access that the IAEA can get," Nuland told reporters. "But it doesn't change the fact that we would consider a satellite launch a violation not only of their UN obligations but of the commitments they made to us."

The deal would see hundreds of tonnes of US food aid sent to impoverished North Korea in exchange for a moratorium on missile and nuclear tests, as well as suspending nuclear work at its Yongbyon reactor.

The deal also opened the way for IAEA inspections of North Korea's nuclear programme, which has gone unmonitored since the country asked agency experts at the reactor to leave and restarted its atomic activities three years ago.

The agency did not detail the terms of the invitation to visit North Korea, such as whether they would involve an in-country discussion of what IAEA experts could do at nuclear sites.

"Nothing has been decided yet,' said Tudor in an email to news organisations. "We will discuss with the DPRK and other parties concerned for the details of the visit," she said, using the acronym for North Korea's formal name, the Democratic People's Republic of Korea.

North Korea is under tough UN sanctions that were tightened in 2009 when it conducted its second nuclear test and launched a long-range rocket. In late 2010, Pyongyang unveiled a uranium enrichment facility that could give it a second route to manufacturing nuclear weapons in addition to a plutonium-based programme at its reactor.

Despite concerns from China, its chief ally, Ri, the senior North Korean nuclear negotiator, reiterated that his country viewed the planned satellite launch as legitimate after holding talks on Monday with his counterpart in Beijing. He said the launch was separate from recent talks with the US over food aid.

"The launching of the satellite is part of our right to develop space programmes," Ri said, warning that North Korea would respond to any threats on its sovereignty.

"Regarding the peaceful purpose of the satellite launching, if others are practising double standards or inappropriately interfere with our sovereign rights, we will be forced to react to it. But we will try our best for these things not to happen," he said.

The US, Japan, Britain and others have urged North Korea to cancel the launch, calling it a threat to diplomatic efforts and warning that it would violate a UN ban on nuclear and missile activity because the same rocket technology can be used for long-range missiles.